1. Field of the Invention
The present invention relates to improvement of a document conveyance apparatus which automatically feeds a document onto a document table (platen glass) of a copier, image reading equipment, etc. and discharges the document after processing from such document table.
2. Description of the Related Art
Generally, the document conveyance apparatus of this type is composed of a document store (paper feeding tray) placed on the side of the document table, document feeding means for feeding the document one by one onto the above document table from such paper feeding tray, document conveyance means placed on the above document table which conveys the document fed from the above document feeding means, places it correctly on the exposure position on the above document table and discharges the document from the above document table upon completion of a prescribed number of exposures, and paper discharging means which collects the documents, for which exposure has been completed, and places them on a discharging paper tray.
This document conveyance apparatus was provided with a document conveyance means which conveyed the document by pressing the document against the platen glass surface with a white endless belt on the platen glass of a copier and also by movement of such belt. In other words, this document conveyance means pressed the document by covering the entire surface of the platen glass with the endless belt and simultaneously conveyed it while generating frictional forces with appropriate places on the document surface via slight slackness therebetween. On account of the above arrangement, there were the following problematic points:
1. Space in the thickness direction became necessary to allow for the belt rotation, thereby increasing the height of the equipment proper, and the equipment became large;
2. Maintenance quality was not satisfactory because of lowering of the pressing force with the passage of time due to fatigue or degradation of the belt and also because of frequent troubles due to lack in elasticity;
3. A large-sized motor of high output had to be used, because the belt was rotated while sliding it on the platen glass.
Applicant of the present invention has earlier improved the above problematic points, and has proposed a document conveyance apparatus which can realize reduction in equipment thickness and improvement in maintenance quality (Japanese patent application No. 3341/1988).
The document conveyance apparatus of the present invention is constructed so as to have low overall apparatus height and also to permit document conveyance without use of an endless belt. A document holding sheet member (white-colored fixing sheet member, hereinafter called the sheet member) is provided along the platen glass surface in the apparatus proper placed above the copier. A document conveyance roller is slidably contacted to the above platen glass surface via holes provided at appropriate places in such sheet member.
The document conveyance roller in the above document conveyance apparatus consists of a multiple number of rollers for conveying documents of various sizes on the platen glass, and each roller will have the rotating force transmitted thereto from the driving source.
In this document conveyance apparatus, the document is normally conveyed into the space between the platen glass surface and the document holding sheet by its conveyor, then such document is sent in the reverse direction, so that the document rear end will run against the stopper board (striking board), for determining and stopping the document at the correction position, then exposure will be made on the document in such striking and stopping conditions.
FIG. 21 is a plan view showing the document sizes and the layout of conveying rollers. In the diagram, the document of various sizes will stop at the striking board 12 in the extreme left of the document table (platen glass) 11, where the document will undergo an exposure process. On the upper surface of the above document table there are provided document conveying rollers 301, 302, 303 and the white-colored sheet member 304 of the document conveyance apparatus.
However, in such document conveyance apparatus, when a document is conveyed toward the striking board on the document table, in the case of a document of the smallest size, for example, a B6 size or a B5 size document, such document will be conveyed under pressure contact, being slidably moved by one set of the document conveying rollers closest to the striking board. In the case of a document of the largest size, for example, an size document, such document will be conveyed under pressure contact, being slidably moved by a number of document conveying roller sets.
In this manner, with respect to documents of each size which are run against the striking board, in the case of a document of small size, its striking force will be small, being run and stricken only by the sliding conveying force of one set of the document conveying rollers closest to the striking. Board the case of a document of medium size and in the case of a document of large size, they are run and stricken by the sliding conveying force of 2 sets or 3 sets of the document conveying rollers. Therefore, the striking force of medium size documents and large size documents against the striking board will become large proportionately with the number of roller sets.
At the time of sending the document backward and stopping it at the striking board, when the striking force of the document caused by each document conveying roller is excessive, the rear end of the document may be folded, wrinkles may be generated in the document, or the document may be set diagonally. Alternately, there may arise such troubles as where the rear end of the document rides on the upper surface of the striking board or the document further passes above the striking board and returns to the paper feeder side.